In the communication technology field, with the constant improvement of the requirement on the future communication by people, the edge frequency spectrum efficiency of the cell is paid more attention to. In the advanced long term evolution (LTE-Advanced) system, in order to further improve the system performance and the frequency spectrum efficiency of the edge user, the Coordinated multi-point transmission/reception (Comp) technology is provided. The Comp technology is that the User Equipment (UE) utilizes the antenna of the multiple access points (AP) to cooperate to transmit and receive information. The Comp technology can solve the problem of the information interference of the cell effectively, thus improving the information capacity and the dependability of the wireless link.
Referring to FIG. 1, one or more access points can be set under one base station or one cell, the multiple points cooperated in the Comp can be multiple access points from one cell and also can be multiple access points from multiple cells. Wherein, the cell includes a primary cell and a cooperation cell of the user (UE) terminal. But because the AP points of the Comp are distributed in different geographical locations, when multiple AP points transmit the downlink data to one UE at the same time, the difference of the time for the data sent from different APs arriving at the UE causes a certain channel delay inequality of the information which reaches the UE. The channel delay inequality will bring the phase rotate deviation of the information frequency domain, and cause the phase that the information reaches the UE to have a certain deviation. Meanwhile, when multiple AP points send the data at the same time, different AP points will have a certain timing synchronization deviation with each other, which makes the time for different AP points to send the data to the same UE to have a certain out-sync. Specifically, in the current Comp technology, there are two precoding feedback realization mechanisms of the information: first is a global precoding, that is, the multiple AP points jointly feed back one global codebook, there is no phase deviation of the information, but only the delay inequality; second is a local precoding+relevant information among the AP points, that is, each AP point correspondingly measures and feeds back one independent codebook respectively, and feeds back the relevant information among the AP points at the same time. Wherein, the relevant information among the AP points includes: the independent Precoding Matrix Indication (PMI) based on the feedback, measuring and feeding back phase calibration information between the two APs, or the feedback channel delay inequality between the two AP points.
Because of the accumulation result of the above-mentioned channel delay inequality and/or the timing synchronization deviation among the AP points, it makes the data sent by different AP points of the Comp to one UE at the same time have a certain channel delay inequality with each other, causing the system performance reduced. Through calibrating the deviation of different AP points, it obtains that there is no deviation in the timing synchronization of the AP points sending the data, the channel delay inequality is zero and the phase deviation is zero, and the system performance will be improved.
In the related art, no matter it is the independent feedback coding of each AP point or the global precoding, the UE feeds back the phase calibration information alone, to overcome the phase rotation deviation of the frequency domain brought by the delay inequality, and the UE needs to feed back the phase calibration information with smaller granularity of the frequency domain, which will make the feedback expense larger; if the delay inequality information is fed back alone, the phase difference problem brought by feeding back the codebook by each AP independently cannot be solved.
In sum, the related art is unable to solve the phase difference problem brought by feeding back the codebook by each AP independently under the condition that the feedback expense is smaller, and unable to solve the problem of the delay inequality among the AP points, therefore, the system performance and the frequency spectrum efficiency are relatively low.